Usage
The average dosage taken by consumers of wheatgrass is 3.5 grams (powder or tablets). Some also have a fresh-squeezed 30 ml shot once daily or for more therapeutic benefits a higher dose up to 2–4 oz taken 1-3 times per day on an empty stomach and before meals. For detoxification, some users may increase their intake to 3–4 times per day. It should be noted that consumers with a poor diet may experience nausea on high dosages of wheatgrass.

Health Claims
Proponents of wheatgrass claim regular ingestion of the plant can

  • improve the digestive system
  • prevent diabetes and heart disease
  • cure constipation
  • detoxify heavy metals from the bloodstream
  • help make menopause more manageable
  • promote general well-being

Wheatgrass Juice vs. Common Vegetables
One of the most popular claims about wheatgrass is that 1 ounce of wheatgrass juice is as nutritionally valuable as 1 kg (2.2 lb) of green vegetables, a ratio of 1:35. In fact, the vitamin and mineral content of 1 ounce of wheatgrass juice is roughly equivalent to the vitamin and mineral content of 1 ounce of fresh vegetables.

Nutrient comparison of 1 oz (28.35 g) of wheatgrass juice, broccoli and spinach.
Nutrient Wheatgrass Juice Broccoli Spinach
Protein 860 mg 800 mg 810 mg
Beta carotene 120 IU 177 IU 2658 IU
Vitamin E 880 mcg 220 mcg 580 mcg
Vitamin C 1 mg 25.3 mg 8 mg
Vitamin B12 0.30 mcg 0 mcg 0 mcg
Phosphorus 21 mg 19 mg 14 mg
Magnesium 8 mg 6 mg 22 mg
Calcium 7.2 mg 13 mg 28 mg
Iron 0.66 mg 0.21 mg 0.77 mg
Potassium 42 mg 90 mg 158 mg
 

Detoxification
Another common claim for wheatgrass is that it promotes detoxification. The limited data in support of that claim also applies to most green vegetables.

Chlorophyll
It has been argued that wheatgrass helps blood flow, digestion and general detoxification of the body. These claims have not been substantiated. Some research however exists that relates diets high in green leafy vegetables, which have high concentrations of chlorophyll, with lower rates of colon cancer.

Source: http://en.wikipedia.org/wiki/Wheatgrass